Rigid panel for making a floor covering

ABSTRACT

The disclosure relates to a multilayer panel for producing a floor covering, comprising a wear layer bonded to a back layer, said back layer being made up of at least a thermoplastic material, a plasticizer and fillers, the wear layer comprising a surface layer made up at least of PVC, said surface layer having a Shore D hardness greater than or equal to 60 and a Young&#39;s modulus greater than or equal to 1000 MPa.

TECHNICAL FIELD

The present disclosure relates to the technical sector of floorcoverings, and more particularly a floor panel for producing a floorcovering or the like. The panel according to the disclosure is in theform of a tile or plank, is made from a plastic such as polyvinylchloride (PVC) and has good mechanical properties.

PRIOR ART

It is well known to produce floor coverings from modular elements in theform of planks or tiles. These modular elements can be glued on thefloor or placed freely, in particular when they have male-femaleassembly means. Such male-female panel connecting or assembly means arein particular described in documents GB 2,256,023, EP 1,026,341, WO2012/004701, EP 2,843,153 or WO 2016/030627.

Floor coverings are in particular known in the form of planks and tilesmade from several layers of plasticized PVC, the latter beingparticularly advantageous because they are easier to transport thanrolls of PVC floor coverings. They are also quick and easy to place.They are thus often used in renovations to cover existing floors.

However, this type of covering generally has poor resistance toindentation, scratching and scraping.

Furthermore, this type of covering does not perform well in terms ofdimensional stability according to the criteria contained in standard NFEN ISO 23999 dated April 2012. Indeed, when this type of covering issubject to major temperature variations, in particular when it is placedbehind picture windows, shrinkage or expansion phenomena may beobserved. These phenomena cause defects to appear, such as doming (thepanels curve and locally unstick from the floor, forming a hump),disconnection of the assembly means, or the appearance of play betweentwo adjacent panels.

To resolve this drawback, one solution may consist of systematicallygluing this type of covering, even if it comprises assembly means, inzones subject to significant temperature variations. However, thismethod is tedious, since it increases the placement time andtechnicality. Additionally, it forces the user to respect a roomtemperature of about 20° C. during placement.

SUMMARY

One aim of the disclosure is therefore to propose a floor panel madefrom PVC for producing a floor covering or the like having very goodperformance in terms of resistance to indentation, abrasion and scrapingwhile retaining, or even improving dimensional stability.

Another aim is to propose a floor panel withstanding a passage of atleast 25,000 cycles of a double band castor chair as defined in standardISO 4918 or NF EN 425.

Another aim is to propose a floor panel classified P4 or even P4Saccording to the U.P.E.C. classification. Another aim is in particularto propose a floor panel having an indentation value less than or equalto 0.20 mm, preferably less than or equal to 0.15 mm between two staticresidual indentation measurements done according to standard NF EN 433.Another aim is to propose a floor panel having scraping values accordingto level r1 or even r2 defined according to the method for “determiningthe scraping resistance_Test Mr.bis” described in e-Notebook no. 3562 bythe Centre Scientifique et Technique du Batiment dated March 2007. Thistest consists of looking for the stress to be applied on a truncatedsteel nail with a 3 mm diameter, after which there is an irreversiblepenetration (critical stress), and the stress beyond which the coveringis perforated (maximum stress). Level r1 is obtained if the maximumstress is greater than or equal to 7 N/mm². Level r2 is obtained if thecritical stress is greater than or equal to 30 N/mm² and if the maximumstress is greater than or equal to 1.5 times the critical stress, whichcorresponds to a maximum stress greater than or equal to 45 N/mm².

To that end, a multilayer panel for producing a floor covering isproposed, said panel comprising a wear layer bonded to a back layer,said back layer being made up of at least a thermoplastic material, aplasticizer and fillers, the wear layer comprising a surface layer madeup at least of PVC, said surface layer having a Shore D hardness greaterthan or equal to 60 and a Young's modulus greater than or equal to 1000MPa.

The wear layer according to the disclosure comprises a surface layerhaving a Shore D hardness greater than or equal to 60 and a Young'smodulus greater than or equal to 1000 MPa. This rigid surface layer isarranged in the upper part of the wear layer, such that the upper faceof the surface layer can be in contact with the user. This surface layeris therefore directly exposed to the wear due to traffic, with theexception of cases where this surface layer is covered with a varnish.Without limitation, the surface layer according to the disclosure may begrained and/or covered with a surface varnish, in particular in order tomake it easier to maintain.

Integrating a surface layer having a Shore D hardness greater than orequal to 60 and a Young's modulus greater than or equal to 1000 MPa madeup of at least PVC in the wear layer of a multilayer panel makes itpossible to improve the properties of resistance to indentation,abrasion and scraping of the panel while retaining or even improving thedimensional stability of the panel. The dimensional stability of thepanel is improved because the surface layer is rigid and makes itpossible to counterbalance the expansion and shrinkage effects of theback layer during major temperature variations, in particular between 0°C. and 50° C. The term rigid means, in the case of the surface layer,that the latter has a Shore D hardness greater than or equal to 60,preferably greater than or equal to 70, and a Young's modulus greaterthan or equal to 1000 MPa, preferably greater than or equal to 1500 MPa.

Advantageously, the surface layer has a Shore D hardness greater than orequal to 70. A Shore D hardness greater than or equal to 70 essentiallymakes it possible to improve the resistance to indentation, abrasion andscraping, the layer being more rigid on the surface.

Advantageously, the surface layer has a Young's modulus greater than orequal to 1500 MPa. A Young's modulus greater than or equal to 1500 MPaessentially makes it possible to improve the resistance to indentation,abrasion and scraping and the dimensional stability of the multilayerpanel, the panel being more rigid as a whole.

Advantageously, the surface layer is transparent. The surface layer maybe transparent or translucent, such that a decorative layer bonded onthe back of the surface layer may be visible through the surface layer.In the case of a transparent or translucent surface layer, thedecoration may be provided by a decorative layer comprised in the wearlayer, and bonded on the back of the surface layer. The decorative layermay in particular consist of a decorative film that may be obtained froma PVC film printed on one of its surfaces. Known printing techniques arein particular rotogravure. The decorative layer may also be printeddirectly on the back of the surface layer. The decorative layer may alsobe obtained from pellets made of PVC, then pressed, by plastisolcoating, by flat die extrusion, calendering or any other technique wellknown by those skilled in the art.

The decorative layer may alternatively be obtained by making a printingcomplex comprising a glass web coated with a PVC plastisol set on bothof its faces. The face intended to be bonded across from the surfacelayer is then printed, for example by rotogravure. The glass webimproves the dimensional stability of the floor covering and increasesthe tear resistance relative to a traditional printed film. Theperforation resistance is also improved compared to a printed film. Sucha printing complex generally has a thickness between 0.5 and 1 mm and asurface density between 700 and 1200 g/mm².

The surface layer may in particular be made translucent by incorporatingpigments or fillers into its composition, in a small enough quantity toallow the observation of a decoration arranged on the back side of saidlayer.

The surface layer may also be made opaque in order to give a decorativefunction to the panel. In this case, the composition of the surfacelayer comprises pigments and/or fillers in a large enough quantity tomake it opaque. Known techniques for obtaining a decoration in thethickness of a surface layer in particular consist of pressing pelletsmade from PVC colored different shades distributed statistically, inorder to obtain non-directional “variegated” decorations. Thesedecorative layers may also be produced by calendaring or extrusion of aset “dry blend”, in particular in order to obtain directional or unified“variegated” decorations. Fillers are in particular inorganic fillers,for example clays, silica, kaolin, talc, and calcium carbonate.

Advantageously, the surface layer comprises between 0% and 90% offillers by weight of the layer, advantageously between 10% and 60% byweight of the layer.

Advantageously, the surface layer comprises impact absorbers.Incorporating impact absorbers makes it possible to make the surfacelayer less brittle, in particular at low temperatures, based on theconsidered applications for the panel according to the disclosure.

Incorporating impact absorbers in particular makes it possible to make arigid layer less brittle at temperatures below 20° C., or even below 10°C., which is not common in a residence, but may cause breaks whenplacing the covering, or during transport and storage operations innon-temperature-controlled zones.

Advantageously, the impact absorbers that may be used are elastomericpolymeric particles. These elastomeric polymeric particles are called“core-shell particles” and are well known by those skilled in the art.They are formed by a “hard” thermoplastic shell, preferably with anacrylate polymer base, for example polymethyl methacrylate (PMMA), andan elastomeric core generally with a butadiene base, oftenco-polymerized with styrene, or with an acrylic base.

Advantageously, the surface layer comprises elastomeric polymericparticles.

To obtain an elastomeric core, examples in particular includeacrylonitrile-butadiene-styrene (ABS) polymers, acrylonitrile styreneacrylate (ASA) polymers, methacrylate-butadiene-styrene (MBS) polymers,methacrylate-acrylonitrile-butadiene-styrene (MABS) polymers,ethylene/vinyl acetate (EVA) and ethylene/vinyl acrylate (E/VAC)copolymers, vinyl chloride/vinyl-acrylate/ethylene (E/VAC/VC) graftedterpolymers, chlorinated polyethylene (CPE); polyurethane elastomers(PUR), butadiene/2-vinylpyridine, butadiene/methyl isoproprenyl ketone,butadiene/fumaric ester copolymers and mixtures thereof.

These impact absorbers thus contain a cross-linked or weaklycross-linked elastomeric core, surrounded by a thermoplastic shell,often a polymethyl methacrylate (PMMA) polymer. A weakly cross-linkedelastomeric core in particular makes it possible to improve the impactresistance of the obtained surface layer. U.S. Pat. Nos. 3,985,703,4,304,709, 6,433,091, EP 1,256,615 or U.S. Pat. No. 6,869,497 inparticular describe such particles, which are thus well known by thoseskilled in the art. Core-shell polymers are available from manysuppliers.

As examples, it is possible to use, as impact absorbers, the MBSClearstrength C301, C303H, C223, C350, C351, E920 or C859 particles fromArkema, MBS C301 and C303H being preferred. The Durastrength D300 orD340 particles from Arkema, which have an acrylic core surrounded by aPMMA envelope, can also be used. Likewise, it is also possible to usethe MBS developed by Rohm and Haas, in particular the Paraloid™ BTA 753,Advastab, or Advalube, the styrene/maleic anhydride copolymers modifiedby a rubber such as the polymers from the Elix 300 series marketed byMonsanto. Other impact absorbers such as the Hytrel 3495 marketed byDuPont, or CPE marketed under the Tyrin brand by DuPont, as well as theline called Kane Ace MX marketed by Kaneka can also be used.

Advantageously, the impact absorbers are polymeric plasticizers.Polymeric plasticizers that can also be used according to the disclosureare the copolymers and terpolymers from the Elvaloy and Elvaloy HPseries marketed by Dupont, the thermoplastic polyurethane (TPU)particles in particular marketed by BASF under the Elastollan line, orby Lanxess under the Baymod line. These TPUs can be aromatic, morepreferably aliphatic, formed from polyether polyols, or more preferablyformed from polyester polyols, formed from caprolactone derivatives orformed from thermoplastic copolyesters.

Advantageously, the surface layer comprises polymeric plasticizers.

The different impact absorbers listed can be used alone or in a mixture.

Preferably and in order to obtain a transparent surface layer, theimpact absorbers are chosen based on their index of refraction so thattheir incorporation does not modify the index of refraction of theobtained composition compared to the index of refraction of the PVCalone. The index of refraction of the incorporated impact absorbers isin particular comprised between 1.52 and 1.55 at 20° C.

Preferably, the proportion of impact absorbers by weight of the surfacelayer is less than 25%, preferably comprised between 2.5% and 15% byweight of the surface layer. The quantity of impact absorbers by weightof the layer depends on the grade of impact absorbers used, and inparticular the chain length of the longest of the polymers forming theimpact absorber. This quantity may easily be adapted by one skilled inthe art based on the glass transition temperature of the composition ofthe obtained surface layer.

According to one particular embodiment of the disclosure, thecomposition of the surface layer has a glass transition temperature (Tg)between 60° C. and 80° C., preferably between 70° C. and 80° C. Thisglass transition temperature above the temperature generally observed ina room likely to receive the public makes it possible to guarantee thatthe surface layer will not soften much under normal usage conditions,which will guarantee the dimensional stability of the entire panelaccording to the disclosure.

Advantageously, the surface layer may be obtained from a compositioncomprising at least one liquid, non-polymeric plasticizer, theproportion of liquid plasticizer by weight of the surface layer beingless than 10%, preferably less than or equal to 5%. A proportion ofliquid plasticizer of less than 10% will increase the rigidity of themultilayer panel while making it possible for this surface layer to beproduced using traditional calendaring or extrusion methods. Aproportion of liquid plasticizer of less than or equal to 5% furtherincreases the rigidity of the multilayer panel as well as the resistanceto indentation, abrasion and scraping and the dimensional stability ofthe panel.

Incorporating a quantity of liquid plasticizer of less than 10% byweight of the surface layer allows the rigid surface layer to be easierto transform and less brittle while retaining good dimensional stabilityproperties. The presence of a low liquid plasticizer level, or less than10% by weight of the surface layer, also facilitates the implementationof the PVC at a temperature of less than or equal to 180° C., thuslimiting the risks of degradation of the material. This property isparticularly advantageous in the methods for manufacturing a surfacelayer by calendaring. Incorporating a quantity of liquid plasticizer ofless than 5%, more preferably between 1 and 5% by weight of the surfacelayer, makes it possible to obtain a better compromise between thedimensional stability, abrasion resistance and scratch resistanceproperties.

According to one particular embodiment of the disclosure, the molecularweight of the PVC used to produce the surface layer, traditionallylinked to the value K or “K-value”, the definition of which is wellknown by those skilled in the art, is comprised between 50 and 85,preferably 50 and 75, and very preferably 50 and 64. This in particularmakes it possible to guarantee that the composition of the rigid PVClayer can be transformed using methods such as calendaring or continuouspressing, at a temperature below or equal to 180° C.

Preferably, the surface layer has a thickness of between 0.1 and 3 mm,preferably between 0.3 and 2.5 mm, more preferably between 0.5 and 2 mm.The thickness of the surface layer may be determined as a function ofthe desired use for the panel according to the disclosure. A surfacelayer whose thickness is comprised between 0.1 mm and 1 mm in particularcorresponds to the traditional thickness of surface layers of LVT(Luxury Vinyl Tile) panels.

Preferably, the surface layer has a thickness of between 5% and 30% ofthe total thickness of the panel. The greater the thickness of thesurface layer is relative to the total thickness of the panel, the morestable the dimensions of the obtained panel will be as a function oftemperature. A minimal thickness of the surface layer will slightlyimprove the dimensional stability of the panel and will make it possibleto obtain a good scratch resistance. By increasing the thickness of thesurface layer, within the limit of 30% of the total thickness of thepanel, the dimensional stability and the indentation resistance of thepanel will be optimized.

According to the disclosure, the back layer may be compact, or foam. Itmay be obtained using any method well known by those skilled in the art,in particular by calendaring, pressing, extrusion or coating. It may beobtained from plasticized PVC. In general and in a manner well known bythose skilled in the art, a back layer may be obtained from acomposition comprising a thermoplastic material such as a thermoplasticpolymer, for example PVC, a plasticizer, fillers and optionallystabilizers, lubricants, additives and pigments. Alternatively, thethermoplastic polymer may be replaced in whole or in part by rubber,either natural or synthetic, linoleum or polyester.

In general, a back layer and a layer of plasticized PVC may be obtainedwith a composition comprising about 30% PVC, about 10% plasticizers,about 5% additives (process aids, stabilizers, pigments) and about 55%fillers. Preferably, a back layer may be obtained from a first backlayer and a second back layer bonded to one another via a reinforcementsuch as a glass web. As an example, the first back layer comprises about33% PVC, 10% plasticizers (DINP), 4% additives (process aids,stabilizers, pigments), 3% PVC particles mixed with glass fibers and 50%fillers; the second back layer comprises about 33% PVC, 10% plasticizers(DINP), 4% additives (process aids, stabilizers, pigments) and 53%fillers.

Preferably, and in order to enhance the mechanical performance andindentation and scraping resistance and to further improve thedimensional stability of the panel over time, the back layer comprises areinforcement. A reinforcement may be obtained from a woven or non-woventextile, or from a glass grid and/or a web, a glass grid and a web beingable to be complexed. By incorporating a surface layer made from rigidPVC into the panel, and depending on the thickness of said surface layerrelative to the total thickness of the panel, it is possible that thedifference in rigidity between the surface layer and the rest of thelayers of the panel may cause doming or curling phenomena, i.e., acurvature of the panel in one direction or the other. This phenomenonappears in response to poor balancing of the mechanical stresses betweenthe layers of the panel. The addition of one or several reinforcementsin the back layer makes it possible to stiffen the back layer and thusbalance the panel as a whole.

A reinforcement has for example the form of a grid or quadrille oftextile yarns of negligible thickness. The textile yarns of saidreinforcement are for example obtained from glass fibers, and arepreferably, separated from each other by 3 mm along the longitudinal andtransverse dimensions and have a linear mass density included between 20g/m and 70 g/m, advantageously between 35 g/m and 50 g/m. Areinforcement may also consist of a web of glass fibers or polyesterfibers with a surface density comprised between 40 g/m² and 100 g/m².

Alternatively or additionally, in order to increase the mechanicalperformance, increase the resistance to indentation and scraping, andfurther improve the dimensional stability of the panel, the back layermay comprise a balancing layer, made up at least of PVC. A balancinglayer in particular makes it possible to balance the tensions in themultilayer panel created by the surface layer according to thedisclosure. Advantageously, the balancing layer is a layer for balancingtensions in the multilayer panel created by the surface layer accordingto the disclosure. The balancing layer is obtained using any meansdescribed for obtaining the surface layer according to the disclosure.

Advantageously, the balancing layer has a Shore D hardness greater thanor equal to 50, advantageously greater than or equal to 60, preferablygreater than or equal to 70, and a Young's modulus greater than or equalto 500 MPa, advantageously greater than or equal to 1000 MPa, preferablygreater than or equal to 1500 MPa. The balancing layer is thus rigidenough, or as rigid as the surface layer, in order to increase therigidity of the panel. The rigidity of the balancing layer may beadapted based on the differences in thickness of the surface andbalancing layers and their compositions.

A balancing layer made up at least of PVC may in particular be obtainedfrom a composition comprising a proportion of liquid plasticizer of lessthan 15% by weight of the layer, preferably less than or equal to 10% byweight of the layer, more preferably less than or equal to 5% by weightof the layer.

Advantageously, the composition of the balancing layer comprises impactabsorbers as previously defined, preferably elastomeric polymericparticles. Preferably, the proportion of impact absorbers in thecomposition of the balancing layer is less than 25% by weight of thebalancing layer, preferably between 2.5% and 15% by weight of thebalancing layer. The quantity of impact absorbers by weight of the layerdepends on the grade of impact absorbers used, and in particular thechain length of the longest of the polymers forming the impact absorber.This quantity may easily be adapted by one skilled in the art based onthe glass transition temperature of the composition of the obtainedbalancing layer.

According to one particular embodiment of the disclosure, thecomposition of the balancing layer has a glass transition temperature(Tg) between 60 and 80° C., preferably between 70 and 80° C. This glasstransition temperature above the temperature generally observed in aroom likely to receive the public makes it possible to guarantee thatthe balancing layer will not soften much under normal usage conditions,which will guarantee the dimensional stability of the entire panelaccording to the disclosure.

Preferably, the back layer is a balancing layer made up at least of PVC.

A balancing layer made up at least of PVC makes it possible to decreasethe difference in rigidity between the surface layer and the rest of thelayers of the panel and thus prevents the appearance of curvingphenomena of the panel. The more the Shore hardness is over 50 and theYoung's modulus is over 500 MPa, the more the rigidity of the obtainedpanel, and therefore its dimensional stability, are increased. Theaddition of one or several balancing layer(s) made from PVC in the backlayer thus makes it possible to stiffen the back layer, and thus tobalance the panel as a whole. This balancing layer may be arranged inthe lower part of the back layer, such that a face of the balancinglayer is in contact with the floor. Alternatively, this balancing layermay be arranged in the central part of the back layer so as to balancethe structure of the product and/or to replace a reinforcement.

Alternatively, this balancing layer may be arranged in the upper part ofthe back layer in contact with the wear layer. Advantageously, thebalancing layer is bonded to the wear layer. In the case where saidbalancing layer is bonded to the wear layer, the resistance toindentation, scratching and scraping is improved. This embodiment is inparticular interesting to decrease the thickness of the surface layer,which generally contains little filler and is therefore more expensiveto produce. Decreasing the thickness of the surface layer limits themechanical performance; adding a balancing layer bonded to the wearlayer therefore makes it possible to compensate this decrease and obtainequivalent resistance to indentation, scratching and scraping. This isparticularly interesting in the case where the floor covering comprisesa decorative film, sandwiched between a rigid surface layer made up atleast of PVC and a balancing layer made up at least of PVC.Advantageously, the wear layer comprises a decorative film, saiddecorative film being in contact with the balancing layer.

Preferably and in order to obtain a balanced back layer as such, a firstbalancing layer made up at least of PVC is arranged in the upper part ofthe back layer and a second balancing layer made from PVC is arranged inthe lower part of the back layer.

In general and in a manner well known by those skilled in the art, thesurface layer according to the disclosure and/or the back layeraccording to the disclosure and/or each of the component layers of thesurface or back layer may be obtained by dry blend calendaring, bypressing formulated pellets (compounds) or dry blend pellets, or byextrusion.

Fillers that may be used are in particular inorganic fillers, forexample clays, silica, kaolin, talc, calcium carbonate.

Advantageously, the balancing layer comprises between 0% and 90% fillersby weight of the layer, advantageously between 10% and 60% by weight ofthe layer.

The non-polymeric liquid plasticizers that may be used in each of thelayers of the floor covering according to the disclosure are inparticular plasticizers such as Diisononyl Phthalate (DINP), DiisodecylPhthalate (DIDP), 2-Ethylhexyl Diphenyl Phosphate (DPO), Dioctylicterephthalate (DOTP), 1,2-Cyclohexane dicarboxylic acid diisononyl ester(DINCH), plasticizers from the benzoate family, plasticizers from theadipate family, plasticizers marketed under the PEVALEN® brand byPerstorp, epoxidized soybean oil (ESBO), epoxy octyl stearate (EOS),entirely or partially biosourced plasticizers, for instance plasticizersfrom the Polysorb® ID 37 line marketed by Roquette Pharma, plasticizersfrom the citrofol line marketed by Jungbunzlauer International AG, orplasticizers from the soft-n-safe line marketed by Danisco. The liquidplasticizers can be used alone or in a mixture.

The panels according to the disclosure assume the form of planks ortiles, each panel comprising an upper face intended to be in contactwith the user, a lower face intended to be in contact with the floor andfour edges. The edges of the panels according to the disclosure can bemachined to have male-female assembly means, making it possible toconnect several panels to one another. Male-female assembly means inparticular refer to means comprising a slot machined on one of the edgesof a panel and configured to be assembled with a tab machined on theopposite edge of an adjacent panel. Male-female assembly means assembledperpendicular to the floor and using machining profiles in the form ofdovetails are also considered. In general, the male-female assemblymeans comprise a first machining profile machined on one edge of a paneland configured to be assembled to a second machining profile machined onan opposite edge of an adjacent panel. The panels thus obtainedgenerally have two pairs of machining profiles, each pair comprising afirst and second machining profile on two opposite edges of a panel. Thefirst and second machining profiles of each pair are not necessarilysimilar, in particular depending on the length of the considered edgeand the desired assembly direction. The assembly of the panels may inparticular be done in a direction perpendicular to the floor in the caseof so-called “vertical” assembly means, in a direction parallel to thefloor in the case of so-called “horizontal” assembly means, or in morecomplex directions, for example by rotation and/or translation of a maleassembly means in a female assembly means. Such assembly means are inparticular described in documents GB 2,256,023, EP 1,026,341, WO2012/004701 or WO 2016/030627. Preferably, once assembled, the assemblymeans block the movement of two panels at once in a vertical direction,i.e., perpendicular to the floor, and in a direction that isperpendicular to the edge of the panel on which the considered assemblymeans is machined and parallel to the plane formed by the floor. Theassembly means and their machining profiles may in particular beobtained by in-line machining, injection molding of the panel or bycutting, in particular by hollow punch.

The panels according to the disclosure have a thickness generallybetween 2.5 mm and 10 mm, preferably between 4 mm and 6 mm. Thisthickness is measured between the upper face of the surface layerintended to be in contact with the user and the lower face of the backlayer intended to be in contact with the floor. The panels according tothe disclosure have a width between 8 cm and 70 cm, preferably between15 cm and 25 cm, and a length between 50 cm and 240 cm, preferablybetween 10 cm and 150 cm.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages will emerge better from the followingdescription, provided as a non-limiting example, in reference to theappended figures, in which:

FIG. 1 schematically illustrates a sectional view of a floor coveringaccording to the disclosure, the wear layer of which comprises at leastone rigid surface layer.

FIG. 2 shows a schematic sectional view of an alternative floor coveringaccording to the disclosure.

FIG. 3 schematically illustrates a sectional view of an alternativefloor covering according to the disclosure, the wear layer of whichcomprises at least one balancing layer obtained from PVC.

FIG. 4 schematically illustrates a sectional view of an alternativefloor covering according to the disclosure, the wear layer of whichcomprises at least one balancing layer obtained from PVC.

FIG. 5 schematically illustrates a sectional view of an alternativefloor covering according to the disclosure, the wear layer of whichcomprises at least one balancing layer obtained from PVC.

FIG. 6 schematically illustrates a sectional view of an alternativefloor covering according to the disclosure, the wear layer of whichcomprises at least one balancing layer obtained from PVC.

DETAILED DESCRIPTION

In reference to FIG. 1, the floor covering (1) according to thedisclosure comprises:

-   -   a wear layer (2), comprising a rigid surface layer (4) having a        Shore D hardness greater than or equal to 60 and a Young's        modulus greater than or equal to 1000 MPa and a decorative layer        (2 a);    -   a back layer (3).

The decorative layer (2 a) may in particular consist of a decorativefilm that may be obtained from a PVC film printed on one of said faces.Known printing techniques are in particular rotogravure. Alternatively,the decorative layer (2 a) may also be obtained from pellets made fromPVC, then pressed, by plastisol coating, by flat die extrusion or bycalendaring.

In general, a back layer (3) traditionally made from plasticizedflexible PVC may be obtained with a composition comprising about 30% byweight of PVC, about 10% by weight of plasticizers, about 5% by weightof additives (process aids, stabilizers, pigments) and about 55% byweight of fillers.

The back layer (3) is for example made up of a first layer made from PVC(3 a) intended to be bonded to the wear layer (2), a second layer (3 c)and a reinforcement (3 b) bonded between the first layer (3 a) and thesecond layer (3 c). The layers (3 a) and (3 c) are for example obtainedfrom filled plasticized PVC and formed by calendaring. The back layer(3) may also be obtained by pressing pellets manufactured from PVC, bycoating with plastisol, or by flat die extrusion. Producing this layerby calendaring nevertheless remains its favored manufacturing method interms of cost and resulting mechanical performance.

Alternatively and in reference to FIG. 2, the floor covering (1)according to the disclosure comprises a first reinforcement (3 b) and asecond reinforcement (3 d), for example in the form of two fiberglassgrids.

Particularly and in reference to FIGS. 3, 4 and 5, the back layer (3)may comprise at least a first balancing layer (3 e) made from PVC. In afirst alternative, according to FIG. 3, said balancing layer is arrangedin the lower part of the back layer (3), such that one face of thebalancing layer (3 e) is in contact with the floor.

Alternatively, said balancing layer (3 e) can be arranged in the upperpart of the back layer (3), as illustrated in FIG. 4, such that a faceof the balancing layer (3 e) is in contact with the wear layer (2). Thisposition of the balancing layer advantageously makes it possible toeliminate the reinforcement while retaining the good dimensionalstability characteristics. This position also makes it possible todecrease the thickness of the rigid surface layer (4) while retainingvery good mechanical properties as well as good resistance toindentation, scratching and scraping, while decreasing the manufacturingcost of the floor covering.

Alternatively and in reference to FIG. 5, the back layer (3) maycomprise at least a first balancing layer (3 e) and a second balancinglayer (3 f) made from PVC. The balancing layers (3 e, 3 f) arerespectively arranged in the lower and upper part of the back layer (3).The first balancing layer (3 e) may in particular be bonded to the wearlayer (2). The second balancing layer (3 f) may in particular bearranged to be in contact with the floor. This particular configurationin particular makes it possible to obtain a balanced and dimensionallystable back layer (3), without having to add a reinforcement.

With the aim of obtaining a particularly stable back layer (3), thelatter may also be made up of a single balancing layer obtained fromPVC.

In reference to FIG. 6, the floor covering (1) according to thedisclosure may also comprise:

-   -   a wear layer (2), comprising a rigid surface layer obtained from        PVC (4) and a decorative layer (2 a)    -   a back layer (3), comprising a balancing layer (3 e) arranged in        the central position and obtained from PVC and bonded between a        first back layer (3 a) and a second back layer (3 c) that are        traditionally obtained from plasticized and filled flexible PVC.

In this example, the balancing layer (3 e) makes it possible to improvethe dimensional stability and the scraping of the obtained floorcovering without needing to use a reinforcement such as a glass web.

EXAMPLES Examples 1 to 3

Tiles according to FIG. 2 are manufactured.

These tiles are obtained by static pressing (3 minutes of heating at180° C. and bars followed by 4 minutes of cooling under 10 bars) of:

-   -   A back layer (3), comprising two layers obtained from        plasticized and shaded flexible PVC pellets (3 a and 3 c), said        pellets being manufactured beforehand by compounding;    -   Two reinforcing glass grids (3 b and 3 d) of about 50 g/m² (68        tex, 200 μm thick) intercalated between the two layers (3 a, 3        c) and between the back layer (3) and the wear layer (2).    -   A wear layer (2) comprising a printed decorative PVC film (2 a)        on which a 2 mm transparent rigid surface layer (4) made from        PVC is laminated.

After cooling to ambient temperature, these tiles are covered with athin layer of acrylate-based varnish (not shown) of about 25 g/m², on acoating line.

The pellets making up the backing sub-layers (3 a and 3 c) comprise thefollowing ingredients, expressed in percentages by weight: 41% PVC, 16%plasticizer (DINP), 2% additives (process aids, thermal stabilizers,pigments) and 41% calcium carbonate (CaCO₃). The characteristics of thebacking sub-layers (3 b, 3 d) are summarized in table 2.

The transparent surface layer (4) is in turn obtained by calendaring adry blend of a rigid PVC-based formula. Three transparent surface layersare obtained from rigid PVC (CU 1, CU 2, CU 3) according to thedisclosure as well as a traditional reference surface layer (CU REF).The compositions of the layers (CU 1, CU 2, CU 3 and CU REF) are givenin table 1. The physicochemical characteristics of said layers are alsogiven in detail in table 2.

Four tiles (examples 1 to 3 and reference) are thus produced from eachof layers CU 1 to CU 3 and CU REF. These tiles are self-leveling, andare generally placed on the floor without glue, owing to a male-femaleassembly system in the form of dovetails.

TABLE 1 composition of the tiles Type/% by weight Example 1 Example 2Example 3 Reference Back layer (3) Flexible PVC Flexible PVC FlexiblePVC Flexible PVC PVC  41%  41%  41%  41% Liquid plasticizer DINP/16%DINP/16% DINP/16% DINP/16% Fillers CaCO₃/41% CaCO₃/41% CaCO₃/41%CaCO₃/41% Additives   2%   2%   2%   2% Rigid PVC Rigid PVC Rigid PVCFlexible PVC Surface layer (4) (CU1) (CU2) (CU3) (CU REF) PVC/K-wert85.4%/K60 85.4%/K50 85.4%/K60 72%/K64 Liquid plasticizers DINCH +DINCH + DINCH + DINCH + ESO/7.2% ESO/7.2% ESO/7.2% ESO/26.7% Additives**1.4% 1.4% 1.4% 1.3% Impact absorbers Clearstrength Clearstrength ElvaloyNone W300/5.9% W300/5.9% 741/5.9%

The additives in particular comprise lubricants, process aids, thermalstabilizers and any pigments.

TABLE 2 Characteristic properties of the obtained tiles Example 1Example 2 Example 3 Reference Layer in question Backing CU 1 rigid CU 2rigid CU 3 rigid CU REF sub-layer (flexible) (3a and 3c) Thickness 4 mm2 mm 2 mm 2 mm 2 mm Appearance Pigmented Transparent TransparentTransparent Transparent Shore D hardness (51 ± 1) (70 ± 4) (66 ± 1) (71± 1) (46 ± 1) Tg (tan δ) in ° C. ⁽¹⁾ 39.74 77.8 74.1 67.8 47.2Elasticity modulus 119 2429 1778 1894 60 (MPa) ⁽²⁾ Maximum force 9 46 3632 21 (MPa) ⁽²⁾ Elongation at break 70 64 64 155 210 (%) ⁽²⁾ Staticindentation Not 0.02 0.03 0.05 0.13 (standard EN applicable 433)*Average Not 0.09 0.15 0.09 0.06 dimensional applicable stability(Standard EN 434)* Scraping resistance Not +++ ++ ++ (<19 N/mm²)(according to applicable (>37 N/mm²) (>34 N/mm²) (>31 N/mm²) CSTBnotebook no. 3562): critical stress ⁽¹⁾ Tg determined by rheology on aflat/flat rheometer of the Thermofisher Haake Mars type, equipped with a25 mm wheel: ramp at 5.2° C./min from 180° C. to 25° C. ⁽²⁾ Mechanicaltraction properties determined according to standard ISO 527 on atraction bench of the Shimadzu autograph AGS-X type traction bench, ondumbbell-shaped samples of 58 mm (length between the jaws) × 5 mm(straight width outside attachments zone) × 2 mm thick, at a speed of 10mm/min.

Regarding the scraping resistance test, the stresses indicated in table2 correspond to the stresses applied for which the wear layer, and inparticular the printed decorative film, were not perforated.

The results demonstrate a very strong improvement of the scrapingresistance for the tiles according to the disclosure, examples 1 to 3all obtaining a resistance greater than 35 N/mm². This stress valuemakes it possible to obtain a tile with level r1, or even r2. The staticindentation of the tiles according to the disclosure is also greatlyreduced owing to the use of a wear layer comprising a layer of rigid PVCaccording to the disclosure.

Examples 4 and 5

Planks according to FIG. 6, corresponding to the construction of LVT(“Luxury Vinyl Tiles”) planks, were manufactured according to table 3,by static pressing (3 minutes of heating at 165° C. and 10 bars followedby 4 minutes of cooling under 10 bars).

-   -   The planks comprise a back layer (3):        -   made entirely from plasticized flexible PVC for the            reference plank (REF 2);        -   made from a stack of a balancing layer made from filled            rigid PVC (3 e) bonded between two inner layers of flexible            PVC (3 a, 3 c);    -   a wear layer (2) comprising a printed decorative PVC film (2 a)        on which a 0.5 mm transparent surface layer (4) is laminated,        made from flexible PVC (reference example 4), or rigid PVC        (example 5). The wear layers of example 4 and reference example        2 copy the composition of the reference wear layer CU REF of the        preceding table 2.

The layers made from flexible PVC (3 a, 3 c) comprise the followingingredients, expressed in percentages by weight: 29% PVC, 9%plasticizers (DINP), 8% additives (process aids, thermal stabilizers,pigments) and 54% calcium carbonate (CaCO₃).

The rigid PVC balancing layer (3 e) comprises the following ingredients,expressed in percentages by weight: 50% PVC, 4.5% plasticizers, 0.5%additives (process aids, thermal stabilizers, pigments), 3.5% impactabsorbers and 41.5% calcium carbonate (CaCO₃).

The physicochemical characteristics of the layers (3 e) and (3 a, 3 c)thus obtained are summarized in table 4.

The transparent surface layer (4) is in turn obtained by calendaring adry blend of a formula with a flexible PVC or rigid PVC base.

The obtained planks are self-weighting, and are therefore generallyplaced on the floor without glue, owing to a male-female assembly systemin the form of clicks, like that described in patent application WO2016/030627 by the applicant.

TABLE 3 composition of the LVT planks Type/% by weight Example 4 Example5 Reference 2 Flexible layer 3a, bonded to the balancing layer 3e bondedto the flexible layer 3c Flexible layer Balancing layer Flexible Backlayer (3) (3a) (3e) layer (3c) Flexible PVC PVC  29%  50%  29%  29%Plasticizer DINP; 9% DINCH + ESO DINP; 9% DINP/9% 4.2% Fillers CaCO₃;54% CaCO₃; 41.5% CaCO₃; 54% CaCO₃/54% Additives 0.5% 0.8% 0.5%   8%Impact absorbers n/a Clearstrength n/a n/a W300: 3.5% Thickness 1.35 mm3 mm 1.35 mm 5.7 mm Flexible PVC (CU Flexible PVC Surface layer (4) REF)Rigid PVC (CU5) (CU REF) PVC/K-value 72%/K64 84%/K50 72%/K64 Totalplasticizer DINCH + ESO/26.7% ESO/4.2% DINCH + ESO/26.7% Other additives1.3% 1.3% 1.3% Impact absorbers None Clearstrength None W300/11.7% n/a:Not applicable

The additives in particular comprise lubricants, process aids, thermalstabilizers and any pigments.

The properties of the various layers making up the obtained planks aresummarized in table 4.

TABLE 4 Characteristic properties of the manufactured LVT layersflexible layer (3a balancing layer Layer in question or 3c) (3e) rigid(CU5) Shore D hardness (66 ± 1) (79 ± 1) (78 ± 1) Tg (tan δ) in ° C.⁽¹⁾54.05 74.2 74.8 Elasticity modulus 337 2001 2408 (MPa)⁽²⁾ Maximum force6 18 51 (MPa)⁽²⁾ Elongation at break 30 4 12.4 (%)⁽²⁾ ⁽¹⁾Tg determinedby rheology on a flat/flat rheometer of the Thermofisher Haake Marstype, equipped with a 25 mm wheel: ramp at 5.2° C./min from 180° C. to25° C. ⁽²⁾Mechanical traction properties determined according tostandard ISO 527 on a traction bench of the Shimadzu Autograph AGS-Xtype, on dumbbell-shaped samples of 58 mm (length between the jaws) × 5mm (straight width outside attachments zone) × 2 mm thick, at a speed of10 mm/min.

The properties of LVT planks manufactured according to the architecturedescribed in table 3 are indicated in table 5:

TABLE 5 Characteristic properties of manufactured LVT planks: Example 4Example 5 Reference 2 Static indentation (standard EN 0.05 0.03 0.29433) Average dimensional stability 0.12 0.08 0.11 (Standard EN 434)Scratch resistance* −/+ +++ −/+ *Scratch resistance evaluatedqualitatively after 10 cycles at 25 rpm, on a linear Taber equipped witha 1 mm tungsten carbide tip.

The results demonstrate that the static indentation of the tilesaccording to the disclosure is reduced owing to the use of a balancinglayer (3 e). The use of a wear layer comprising a layer of rigid PVCaccording to the disclosure in example 5 also makes it possible toimprove the scratch resistance greatly.

The invention claimed is:
 1. A rigid multilayer panel for making a floorcovering comprising, a wear layer bonded to a back layer, wherein theback layer comprises a face configured to be in contact with a floor andbeing free of glue, wherein the multilayer panel has edges, and theedges of the multilayer panel have male-female assembly means configuredto connect several multilayer panels to one another, wherein the backlayer comprises a first back layer made from plasticized and filledflexible PVC, and a balancing layer arranged in an upper part of theback layer, the balancing layer is made up at least of PVC obtained froma composition comprising a proportion of liquid plasticizer of less than15% by weight of the balancing layer, the balancing layer is bonded tothe wear layer, and the balancing layer has a Shore D hardness greaterthan or equal to 50 and a Young's modulus greater than or equal to 500MPa, wherein the wear layer comprises a surface layer derived from atleast polyvinyl chloride (PVC), the surface layer having: a Shore Dhardness greater than or equal to 60, a Young's modulus greater than orequal to 1000 MPa, and a glass transition temperature (Tg) between 60°C. and 80° C.
 2. The panel according to claim 1, wherein the surfacelayer has a Shore D hardness greater than or equal to
 70. 3. The panelaccording to claim 1, wherein the surface layer has a Young's modulusgreater than or equal to 1500 MPa.
 4. The panel according to claim 1,wherein the surface layer is transparent.
 5. The panel according toclaim 1, wherein the surface layer comprises impact absorbers.
 6. Thepanel according to claim 5, wherein the impact absorbers are present inan amount of less than 25%, by weight of the surface layer.
 7. The panelaccording to claim 5, wherein the impact absorbers are present in anamount of between 2.5% and 15%, by weight of the surface layer.
 8. Thepanel according to claim 5, wherein the impact absorbers are elastomericpolymeric particles.
 9. The panel according to claim 5, wherein theimpact absorbers are polymeric plasticizers.
 10. The panel according toclaim 1, wherein the surface layer has a glass transition temperature(Tg) between 70° C. and 80° C.
 11. The panel according to claim 1,wherein a composition of the surface layer comprises at least one liquidplasticizer present in an amount of less than 10%, by weight of thesurface layer.
 12. The panel according to claim 11, wherein the liquidplasticizer is present in an amount of less than or equal to 5% byweight of the surface layer.
 13. The panel according to claim 1, whereinthe surface layer has a thickness of between 0.1 and 3 mm.
 14. The panelaccording to claim 1, wherein the surface layer has a thickness ofbetween 0.3 and 2.5 mm.
 15. The panel according to claim 1, wherein thesurface layer has a thickness of between 5 and 30% of the totalthickness of the panel.
 16. The panel according to claim 1, wherein thewear layer comprises a decorative film, the decorative film being incontact with the balancing layer.
 17. The panel according to claim 1,wherein the composition of the balancing layer has a glass transitiontemperature (Tg) between 60° C. and 80° C.
 18. The panel according toclaim 1, having an indentation value less than or equal to 0.20 mm,between two static residual indentation measurements done according tostandard NF EN 433, and having a resistance to perforation of the paneluntil a maximum stress equal to 7 N/mm² applied on the panel by atruncated steel nail with a 3 mm diameter.
 19. A rigid multilayer panelfor making a floor covering comprising, a wear layer bonded to a backlayer, wherein the back layer comprises a face configured to be incontact with a floor and being free of glue, wherein the multilayerpanel has edges, and the edges of the multilayer panel have male-femaleassembly means configured to connect several multilayer panels to oneanother, wherein the back layer comprises a first back layer made fromplasticized and filled flexible PVC, and a balancing layer arranged inan upper part of the back layer, the balancing layer is made up at leastof PVC obtained from a composition comprising a proportion of liquidplasticizer of less than 15% by weight of the balancing layer, thebalancing layer is bonded to the wear layer, and the balancing layer hasa Shore D hardness greater than or equal to 50 and a Young's modulusgreater than or equal to 500 MPa, wherein the wear layer comprises asurface layer derived from at least polyvinyl chloride (PVC), thesurface layer having: a Shore D hardness greater than or equal to 60, aYoung's modulus greater than or equal to 1000 MPa, a glass transitiontemperature (Tg) between 60° C. and 80° C., a liquid plasticizer presentin an amount of less than 10%, by weight of the surface layer.
 20. Arigid multilayer panel for making a floor covering comprising, a wearlayer bonded to a back layer, wherein the back layer comprises a faceconfigured to be in contact with a floor and being free of glue, whereinthe multilayer panel has edges, and the edges of the multilayer panelhave male-female assembly means configured to connect several multilayerpanels to one another, wherein the back layer comprises a first backlayer made from plasticized and filled flexible PVC, and a balancinglayer arranged in an upper part of the back layer, the balancing layeris made up at least of PVC obtained from a composition comprising aproportion of liquid plasticizer of less than 15% by weight of thebalancing layer, the balancing layer is bonded to the wear layer, andthe balancing layer has a Shore D hardness greater than or equal to 50and a Young's modulus greater than or equal to 500 MPa, wherein the wearlayer comprises a surface layer derived from at least polyvinyl chloride(PVC), the surface layer having: a Shore D hardness greater than orequal to 60, a Young's modulus greater than or equal to 1000 MPa, aglass transition temperature (Tg) between 60° C. and 80° C., a liquidplasticizer present in an amount from 1% to 10%, by weight of thesurface layer.